To analyze the fate of 2,4,6-trinitrotoluene (TNT) and its reduction products, a TNT-contaminated soil (350 mg TNT/ kg dry soil) was spiked with [ring-UL-14.C]TNT and treated in a laboratory slurry reactor. During an anaerobic/aerobic treatment, the total radioactivity measured in the supernatant and methanolic soil extracts decreased to 2 per cent. The decrease corresponded to an increase of strongly bound radioactivity to the soil. Throughout the whole treatment process, mineralization of TNT was not observed. During the reductive process, unidentified polar substances increased to a maximum amount of 23.2 per cent of the total radioactivity on the day after the start of the experiment. After the end of the anaerobic phase, still 9.7 per cent of the radioactivity was found in this fraction. Only during the aerobic phase did the polar substances disappear completely. The irreversible character of the binding of the reduced metabolites of TNT to the soil was indicated by the failure of desorption even under rigorous and longterm extraction conditions. A significant release of radioactivity could be measured only by using high concentrations of HCl (5.N) or EDTA (12.5 per cent and 5.9 per cent, respectively). However, in none of the extracts were TNT or any reduced metabolites detected by HPLC and 14.C-radiocounting. Size-exclusion chromatography of humic acids extracted from the treated soil indicated that the metabolites of TNT were evenly bound to the complete range of molecular size of the humic acids

Anaerobic treatment of originally contaminated soil from a former ammunition plant was carried out in a laboratory slurry reactor. While fermenting glucose to ethanol, acetate, and propionate, the anaerobic bacteria completely reduced the nitro groups of 2,4,6-trinitrotoluene (TNT) and aminodinitrotoluenes, which led to a complete and irreversible binding of the reduced products to the soil. 2,4-Dinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine were also reduced in the soil slurry and were no longer detectable after the anaerobic treatment. To mineralize the fermentation products, a subsequent aerobic treatment was necessary to complete the bioremediation process. This bioremediation process was tested in a technical scale at Hessisch Lichtenau-Hirschhagen, Germany. A sludge reactor (Terranox system) was filled with 18 m 3 of contaminated soil (main contaminants were TNT, 2,4dinitrotoluene, hexahydro-1,3,5-trinitro-1,3,5-triazine) and 10 m 3 of water. The anaerobic stage was carried out by periodical feeding of sucrose. The sludge was subsequently dewatered and treated aerobically. Chemical analysis revealed an overall reduction of more than 99% of the contaminants. Ecotoxicological tests performed with various aquatic systems (luminescent bacteria, daphnids, algae) and terrestrial systems (respiring bacteria, nitrifying bacteria, cress plants, earth worms) showed that residual toxicity could not be detected after the anaerobic/aerobic treatment.

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